This invention relates to multi-layered coextruded materials and, in particular, to composite multi-layered materials containing carbonate polymers.
It has become highly desirable to employ thermoplastic materials in extruded sheet applications, and in particular, transparent sheet applications. For example, carbonate polymers derived from reactions of dihydroxyorganic compounds, particularly the dihydric phenols and carbonic acid derivatives such as phosgene, have found extensive commercial application because of their excellent physical properties. These thermoplastic polymers appear to be particularly suitable for the manufacture of molded and extruded articles, wherein impact strength, rigidity, toughness, heat resistance, transparency and excellent electrical properties are required.
Unfortunately, however, such thermoplastic polymers are scratch and mar sensitive. This scratch and mar sensitivity introduces notches to the carbonate polymer materials and adversely affects the physical properties of the molded or extruded articles, such as impact resistance. It has been found desirable to blend less expensive thermoplastics with the carbonate polymer materials, and molding or extruding the resulting composition. However, properties such as impact strength and transparency are often deleteriously affected.
It is desirable to prepare thermoplastic sheets wherein a plurality of components are arranged in laminar fashion to provide the desired good physical characteristics. Unfortunately, the laminated layers are not generally prepared using coextrusion techniques, and the products comprise layers that are individually relatively thick, or the number of layers is relatively small.
In view of the deficiencies in the prior art, it would be highly desirable to produce an impact resistant, generally notch insensitive, multi-layer extruded article which can be employed in glazing and transparent sheet applications.